To mount pushers on the middle part of a watch, it is known to fix a pusher body in a housing, generally provided on the edge of the case, and then to assemble the other constituent elements of the pusher once the pusher body has been driven or screwed into the middle part of the watch.
Given that each component of the pusher has to be assembled individually on the middle part outside of a specialised pusher workshop, the assembly is first of all relatively tedious, since it is not performed by specialists in this type of component, and relatively time-consuming. Secondly, since none of the functional parts are pre-assembled, it is impossible to test the completely assembled pusher before it is actually mounted on the middle part of the watch. Thus, with this assembly solution, it is not possible to check the sealing properties and travel setting of the pusher in a satisfactory manner prior to integration in the case.
To simplify assembly, for screw-in pushers, there exist tubes pre-fitted with sealing gaskets so that the sealing part is pre-assembled. In this case, the tube is screwed into the middle part in a first step, and then the stem is screwed in from the inside in a second step after the return spring of the pusher has been positioned and the pusher head has been pushed to the end-of-travel position. However, the drawback of this solution is that the sealing gaskets are liable to be damaged when the pusher stem is mounted, especially when this operation is not performed by a pusher specialist, and this solution does not allow the sealing and operating travel of the pusher to be pre-tested.
In order to overcome the drawbacks associated with the provision of individual components for pushers prior to the assembly thereof on the middle part of a watch, CH Patent No 692255 proposes a modular assembly solution, wherein a pusher is entirely assembled prior to mounting on the middle part, and then screwed in from the inside in a watch case using a tool acting on the pusher body. The drawback of this solution, however, is that it only applies to screw-in pushers, which must have a cylindrical head, particularly when there is no degree of freedom in rotation between the pusher body and the head.
There is consequently a need for an assembly method which is free of these known limitations.